The present invention relates to sensor system for use at airports and the like. More particularly the invention relates to a magnetic sensor and signal processing system to provide reliable detection of vehicles at specific locations on an area such as an airport.
The presence of vehicles on airport surfaces is currently being monitored visually and by radio contact with various air traffic controllers and others such as baggage handling operations. As air transportation has increased in traffic at major domestic airports, the number and types of vehicles, both aircraft and ground vehicles, has increased rapidly and requires extreme vigilance. Relying on human observation and reporting, however, leaves open the possibility of an aircraft, fuel truck, baggage tractor or other vehicles being in the wrong place at the wrong time.
Concern at major airports where many vehicles and a high potential population density on the runways has been sufficient for extremely costly and complicated systems to be devised to monitor runway traffic. However, at smaller airports, the cost of such as system is prohibitive, leaving the safety of the runways to visual observation exclusively. Even with less traffic, there is still a risk due to fewer personnel being employed to monitor the runways.
Several prior art efforts have been made to improve airport monitoring. Smith U.S. Pat. No. 4,122,522 discloses an aircraft ground monitoring system used when aircraft are taking off or landing, and involves a very complicated design taking into account actual and predicted velocity and the like. Kawashima et. al. U.S. Pat. No. 5,027,114 discloses a ground guidance system using loop coils buried in portions of a taxi way for aircraft. A change in self-inductance of the loop coils provides a signal indicating the presence or absence of an airplane, while also including a fail-safe structure. The loop coils are described on column 2, beginning at line 25, as having the side parallel to the traffic is longer than an automobile but smaller than the aircraft length. The sensor coils overlap for continuous monitoring of a given aircraft, in part to eliminate the activation by an automobile that is too short to be in two coils. Kawashima uses complicated circuitry processing data from sensors that discriminate between cars and planes.
Pilley et. al. U.S. Pat. No. 6,182,005, (and its related U.S. Pat. Nos. 5,548,515; 6,006,158; and 6,195,609) represent a very exhaustively complicated airport guidance and safety system, and uses a variety of means for locating and guiding aircraft and vehicles such as trucks and the like. Pilley et. al. does not attempt to monitor the presence or absence of any vehicle at given locations. Pilley et. al does require each vehicle to have the capability to transmit a minimum of several signals.
Murga U.S. Pat. No. 4,845,629 discloses the use of infra-red, telemetric sensors. Runyon et al. U.S. Pat. Nos. 5,485,151 and 5,969,642 disclose the use of microwave transmitters and receivers as presence detectors. Kato et al. U.S. Pat. No. 5,508,697 also transmits electromagnetic waves that are interrupted by the presence of an aircraft. Brodeur et al. U.S. Pat. No. 6,195,020 discloses the use of magnetometer sensors at railroad crossings.
It would be of great advantage in the art if a simple and effective system could be devised that would indicate the presence of a vehicle at a specific location on the airport surface.
It would be another advantage in the art if such information could be easily transmitted to the control tower even when the location is in a tower or ground radar blind spot.
Other advantages will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, the present invention provides a vehicle detecting system for use on a specific location such as an airport. The system includes a sensor string crossing the path of travel at the location, preferably perpendicular to that direction of travel. The string includes at least one magnetic field sensor and preferably a plurality sufficient to provide magnetic field detection across the location to give complete and even overlapping coverage. Also provided is a transmitter for transmitting signals from the at least one sensor to a monitoring point.
The transmitter can employ a control unit for receiving the signals and a sender for sending the signals to the monitoring point. The preferred magnetic field sensor is a magnetoresistive sensor, and most preferred is a three-axis magnetoresistive sensor having a field range of at least xc2x15 gauss.
In most applications, the sensor string is operably positioned in a groove in the surface so as to avoid wear and tear on the sensor string and, to a lesser extent, the vehicles passing through the location. The monitoring point normally will include a display and control system.